function display(value, fallback = '-') {
    if (value === undefined || value === null || value === '') return fallback
    return String(value)
}

function formatTime(time = Date.now()) {
    return new Date(Number(time) || Date.now()).toLocaleString('zh-CN', {
        year: 'numeric',
        month: '2-digit',
        day: '2-digit',
        hour: '2-digit',
        minute: '2-digit'
    })
}

function formatSecondsToMinSec(totalSeconds) {
    const seconds = Number(totalSeconds) || 0
    if (seconds <= 0) return '-'
    const minutes = Math.floor(seconds / 60)
    const remain = Math.floor(seconds % 60)
    return `${minutes}分${String(remain).padStart(2, '0')}秒`
}

function calculatePace(seconds, kilometers) {
    const totalSeconds = Number(seconds) || 0
    const distance = Number(kilometers) || 0
    if (totalSeconds <= 0 || distance <= 0) return '-'
    const paceInSeconds = totalSeconds / distance
    const minutes = Math.floor(paceInSeconds / 60)
    const remain = Math.round(paceInSeconds % 60)
    return `${minutes}'${String(remain).padStart(2, '0')}''`
}

function divider() {
    return '\n---\n'
}

function kv(label, value) {
    return `> **${label}**：${display(value)}`
}

function buildUpdateSuccess(data = {}) {
    const autoNote = Number(data.auto_run) === 0
        ? '当前未开启自动乐跑。如需跑步，请登录 RunForge 后手动发起。'
        : '已为您开启自动乐跑，系统将按计划代为完成跑步任务，请留意后续提醒。'

    return [
        `## ✅ 乐跑账号信息已更新`,
        '',
        `${display(data.name, '同学')}，您的乐跑账号登录信息已更新成功。`,
        divider(),
        kv('学号', data.account),
        kv('年级', data.grade_id),
        kv('学院', data.academy_name),
        kv('更新时间', formatTime()),
        divider(),
        `**自动乐跑状态**  \n${autoNote}`,
        '',
        `> 请在当前登录乐跑账号的设备上使用「智慧体育」小程序；请勿在其他设备登录该小程序，以免登录状态失效并需重新绑定。`
    ].join('\n')
}

function buildRunSuccess(data = {}) {
    const targetCount = Number(data.target_count) || 0
    const totalNum = Number(data.total_num) || 0
    const timeSec = Number(data.time ?? data.used_time) || 0
    const distanceKm = Number(data.distance) || 0
    const goalLines = targetCount > 0
        ? [kv('目标次数', `${targetCount} 次`), kv('累计次数', `${totalNum} 次`)]
        : [kv('累计次数', `${totalNum} 次`)]

    return [
        `## ✅ 乐跑成功通知`,
        '',
        `${display(data.name, '同学')}，系统已成功代您完成一次乐跑。`,
        divider(),
        kv('学号', data.account),
        kv('跑区', data.pass_tit || data.run_zone_name),
        kv('用时', formatSecondsToMinSec(timeSec)),
        kv('平均配速', calculatePace(timeSec, distanceKm)),
        kv('距离', distanceKm > 0 ? `${distanceKm} km` : '-'),
        ...goalLines,
        kv('完成时间', formatTime()),
        divider(),
        `> 若已开启自动乐跑，请勿在除更新乐跑账号信息以外的其他设备登录「智慧体育」小程序，以免登录状态失效。`
    ].join('\n')
}

function buildRunFail(data = {}) {
    return [
        `## ❌ 乐跑未能完成`,
        '',
        `${display(data.name || data.account, '同学')}，系统在尝试执行乐跑任务时未成功。`,
        divider(),
        kv('学号', data.account),
        kv('时间', formatTime()),
        kv('原因', data.reason || '系统繁忙，请稍后再试'),
        divider(),
        `> 若为登录失效，请在 RunForge 乐跑登录器中重新完成登录后再试。若问题持续存在，请联系 RunForge 客服并说明学号与失败时间。`
    ].join('\n')
}

function buildTargetComplete(data = {}) {
    return [
        `## 🏁 乐跑目标已全部完成`,
        '',
        `${display(data.name || data.account, '同学')}，您设定的乐跑目标已全部完成，系统已为您关闭自动乐跑功能。`,
        divider(),
        kv('学号', data.account),
        kv('目标次数', `${display(data.target_count, 0)} 次`),
        kv('累计次数', `${display(data.total_num, 0)} 次`),
        kv('完成时间', formatTime()),
        divider(),
        `如仍需跑步，可在 RunForge 中按需重新开启相关功能。`
    ].join('\n')
}

module.exports = {
    buildUpdateSuccess,
    buildRunSuccess,
    buildRunFail,
    buildTargetComplete
}